export function throttle(fn, interval) {
  var last;
  var timer;
  return function () {
      var th = this;
      var args = arguments;
      var now = +new Date();
      if (last && now - last < interval) {
          clearTimeout(timer);
          timer = setTimeout(function () {
              last = now;
              fn.apply(th, args);
          }, interval);
      } else {
          last = now;
          fn.apply(th, args);
      }
  }
}
